Amide compositions stabilized with alkylated diphenyl amines



United States Patent US. Cl. 260-453 Int. (:1. 008;; 51/60, 41/02 3 Claims ABSTRACT OF THE DISCLOSURE A stabilized polyamide composition comprising a synthetic, high molecular weight polyamide and a minor amount of an organic amine of the formula CH-C H3 wherein R is a branched alkyl radical of 3-4 carbon atoms. A process for preparing the polyamide composition described above. This composition is particularly useful in stabilizing polyamides which are employed in the preparation of fibers against the degrading elfects of oxygen and heat.

This invention relates to a high molecular polyamide composition stabilised against atmospheric degradation at elevated temperatures.

High molecular weight polyamides can be stabilised more particularly against the effects of heat and oxygen, by a number of compounds which are incorporated or worked into the polyamides in quantities of, generally, 0.1 to 5% by weight.

For example, it has already been proposed to stabilise polyamides with small quantities of N-aryl substituted polyamines. In addition, tertiary and aromatic amines have also been used as stabilisers. Water-insoluble diaryl ketone condensation products have been described as stabilisers against the action of hot water. Apart, however, from the fact that the stabilising effect of many of these amines is far from satisfactory, discolouration of the polyamide is a frequent occurrence.

We have now found that a polycaprolactam composition containing amino compounds as stabilizers against the eifects of heat and oxygen shows hardly any discolouration. According to the present invention amino compounds corresponding to the formula C LEI-CH3 3,425,985 Patented Feb. 4, 1969 in which R is a branched alkyl radical with 3 or 4 carbon atoms, are used as the stabilisers.

These amino compounds are incorporated or worked into the polyamide in quantities from 0.05 to 10% by weight, and preferably in quantities of 0.1 to 5% by weight, in order to obtain the desired stabilising effect. The compounds used in accordance with the invention as stabilisers for polyamides, can be prepared in known manner by reacting diphenylamine with suitable isoolefins and styrene, for example by reacting diphenylamine with isobutylene and styrene. The polyamides stabilised with these amines, in particular polycaprolactams of high molecular weight, are particularly suitable for the production of shaped bodies, for example moulding and fibre products.

The stabilized polyamides are synthetic linear polyamides having molecular weights of 10,000 and higher, especially suitable for fibre formation. The most common polyamides are polycaprolatcam and polyhexamethylenediamine adipate, but other polyamides are also useful for stabilizing.

The stabilisers used in accordance with the invention may be incorporated or worked into the polyamide by tumbling the completed polyamide granulate with the stabiliser, and homogenising the resulting mixture by means of an eXtr-uder. If desired, the melt thus obtained may be directly injection-moulded, or further processed into a fibre-liked material. Alternatively, the melt containing the stabiliser may be re-drawn in filament form into a water bath, chopped up again into granules and then dried. Another method of working the stabiliser into the polyamide melt comprises adding the stabiliser at a given time, before, during or after polymerisation.

Where a continuous-cycle polymerisation plant is available, the stabiliser may even be added directly before the finished polyamide is spun off.

The preparation of the stabiliser preferably used in accordance with the invention is described in the following example:

An autoclave is filled with 506 g. (3 mols) of diphenylamine and 50 g. of acid fullers earth (Tonsil kl0), and is then heated to 270 C. over a period of minutes, after 325 cc. of isobutylene have been pumped into it. When the reaction temperature has been reached, fresh isobutylene is pumped in over a period of 2 hours until :a total of 561 g. (10 mols) of isobutylene is present. The autoclave is kept at 270 C. for another 3 hours and, after cooling to 190 C., 156 g. (1.5 mols) of styrene are pumped in over a period of 30 minutes. The autoclave is kept at 190 C. for 1 hours and, after cooling to approximately C., the acid fullers earth is removed from the mixture by means of a pressure-type suction filter. Yield: 1095 g. of an amber-coloured viscous liquid.

Analysis for Calculated: C, 85.7, H, 9.71, N, 4.54. Found: C, 86.05, H, 9.82, N, 4.50.

The following examples illustrate the invention more particularly.

(CHzhC-Q-NH-Q CHI-CH:

are added to 100 parts of polycaprolactam with a relative viscosity of 3.0 to 3.1 (measured at 25 C. on a 1% solution in m-cresol), which had been polymerised, extracted and dried as known per se. The amine is tumble-mixed with the granulate and homogeneously incorporated by means of an extruder. The resulting melt is drawn into a 2.5 mm.-thick filament in a water bath, chopped up into granules and dried. The chips of polycaprolactam containing the stabiliser are spun in known manner into rayon of 840/140 den. and then stretched. The resulting rayon has normal tensile strengths of approximately 8 g./ den. at a breaking elongation of 16.5% is almost white in colour and only darkened to a limited extent, even on exposure to light.

In order to test the dimensional stability of the filaments under heat, they were exposed to a temperature of 145 C. under a load of 3.7 g./den. until they failed. The

Stabiliser Chemical composition Di-fi-naphthyl-p-phenylene diamine N-phenyl-N -cyclohexyl-p-phenylene diamin N -phenyl-N -isopropy1-p-phenylene diamine time interval up to failure is then measured. For comparison, other filaments were tested, some without stabilisers and some containing known heat stabilisers. Compared with the known diphenylamine stabilisers, the stabiliser according to the invention exhibits far superior thermal stability and colour stability. Compared with stabilisers based on substituted p-phenylene diamines, the polyamides provided with the stabilisers according to the invention exhibit considerably better colour stability (Table 1).

Table 1 is a comparison between the stabilisers according to the invention and some known stabilisers. In each case, the polyamide contains the stabilisers in a quantitty of 0.5% by weight.

nestabiliser according to i nvention Relative viscosity of the starting material 4 Example 2 Table 2 illustrates the effect of atmospheric oxygen at elevated temperature on fairly thick-walled polycaprolactam mouldings in the presence of stabilisers, in comparison with a non-stabilised polyamide and with a polycaprolactam provided with an amine corresponding to the formula GEL-C 3 For this purpose, the stabilisers were each incorporated into the polycaprolactam in quantities of 0.5%, as described above. Filaments 2.5 mm.-thick to 3 mm.-thick were prepared by spinning the melt into a water bath and were then chopped up into granules and dried. The granulate is then exposed to atmospheric oxygen at 150 C., and its relative viscosity is measured at the beginning of the test, after 144 hours, 500 hours and 1000 hours, respectively. The result is given in Table 2 as the percentage decrease in the relative viscosity after hours alongside the other relative viscosity data. The relative solution viscosity is measured on a 1% by weight solution in mcresol at 25 C.

TABLE 2 144 hrs. 1,000 hrs.

Percentage decrease in the relative viscosity after 1,000 hours 500 hrs.

Example 3 Polycaprolactam with a relative viscosity of 3.0 to 3.1 which, following size-reduction, was separated from the monomeric components by extraction with water and then dried, is intimately mixed in a melt extruder with 0.5% by weight of the stabiliser according to the invention as used in Example 1 and the resulting mixture is chopped up. The chips, mixed with the stabiliser, are spun in known manner into a rayon of 840/ den. and then stretched. The resulting rayon has a normal ultimate tensile strength of approximately 8 g./ den. and a breaking elongation of 16.5% is almost white in colour and only darkens to a limited extent on exposure to light.

TABLE 1 Change in the Thermal Colour of the colour of the stability test stabiliser chemical composition rayon rayon on at 0., exposure to duration light in hours None- White. N 2. 02. 5 stabiliser according to the invention- Almost white- Slight 26. 7 Diphenylamine treated with styrene ac- Pale yellow- Deep blue- 9. 3

cording to German Pat. 895,973. 4,4-diisooctyl diphenylamine ace. to U.S. Light grey- Brownish- 12. 1

Patent 2,530,769. 2-m9 'captnhon imirla nle White Nnnn 6, 3 Di-B-naphthyl-p-phenyiene diamine Pale brown. Brown 29. 8 Nhphenyl-N-cyclohexy1-p-phenylene do.-.-.-.-. Dark brown.-. 31.4

iamine. N-phenyl- -isopropy1-p-phenylene -...-do .-do 31. 9

diamine.

To test the dimensional stability of the filaments under weight of at least 10,000 and a stabilizing amount of heat, they were exposed to a temperature of 145 C. under an aromatic amine of the formula a load of 2.7 g./den. until they failed. The time interval 0 before failure is then measured. For comparison, other filaments were tested, some without stabilisers and some Q containing known heat stabilisers. 5 5 5 The following table shows that, compared with stabi- 03-038 lisers based on the same class of compounds, the stabiliser according to the invention exhibits far superior thermostability and colour stability and, compared with stabilisers based on substituted p-phenylene diamine, far superior colour stability and, above all, only limited discolouration. 2. A stabilized polyamide composition according to claim 1, wherein the polyamide is poly-e-caprolactam.

TABLE 3 Change in Thermal Colour of colour on stability test stabiliser the rayon exposure to at 145 0.,

light duration in hours None White None 2. 0-2. 5 Stabillser according to the invention Almost white- Slight 26. 7 Diphenylamine treated with styrene Pale yellow--- Deep blue 9.3

according to German Patent 895,973. 4,4-diisooctyl diphenylamine according Pale grey Brownish.-. 12. 1

to U.S. Patent 2,530,769. 2-me captohpn1imid fl'lfliP Whlte- None 6 3 Di-B-naphthyl-p-phenylene diamine- Pale brown- .Brown 29. 8 N-phenyl-N'-cyclohexyl-p-phenylene do Dark btown 31. 4

diamine. N-phenyl-N'-isopropyl-p-pheny1ene -.d0 -do 31. 9

diamine.

30 3. A stabilized polyamide composition according to What we claim is: claim 1, wherein the polyamide contains 0.05 to 10% by 1. A stabilized polyamide composition comprising a weightcalculated on the polyamide eomposition-of the synthetic, fiber-forming polyamide having a molecular aromatic amine.

References Cited UNITED STATES PATENTS 2,530,769 1/ 1950 Hollis 260--45.9 3,003,995 10/ 1961 Schule 260-45.9 3,349,110 10/1967 Cyba 260-459 DONALD E. CZAIA, Primary Examiner.

H. E. TAYLOR, 1a., Assistant Examiner.

U.S. Cl. X.R. 

